Manufacture of halogenated pyridine derivatives

ABSTRACT

A process for the manufacture of a chloropyridine which comprises interacting -caprolactam with chlorine in the vapor phase at a temperature of at least 250*C.

v v United States Patent 1 [111 3,725,414

Bowden et a]. 1 Apr. 3,1973

[54] MANUFACTURE OF HALQGENATED [58] Field of Search ..260/290 PYRIDINE DERIVATIVES [75] Inventors: Roy Dennis Bowden; Thomas [56] References Cited y, Seaton, both of Runcorn, England OTHER PUBLICATIONS [73] Assignee: Imperial Chemical Industries Houben-Weyl, Methoden der Organishen Chemie,

Limited, London, England Vol. 5/3 p. 727 (1962) [22] Filed: 1971 Primary Examiner-Harry'l. Moatz [2]] Appl. No.: 172,266 Attorney-Cushman, Darby & Cushman [30] Foreign Application Priority Data [57] ABSTRACT 12 A process for the manufacture of a chloropyridine May 4, 1971 Great Br ta n ,90 2/7l which comprises interacting caprolactam with Aug. 19, Great Britain chlorine in the p r phase a a tempe of at l t 250C. 52 US. Cl ..260/290 HL eas v [51] Int. Cl. ..C07d 31/26 7 Claims, No Drawings at an elevated temperature.

I general theupper limit to the proportion of 1 MANUFACTURE OF DERIVATIVES This invention relates to 'the' manufacture of halogenated pyridine derivatives, and more particularly I to the manufacture of chloropyridines.

Previously known methods of producing chloropy idines have relied-upon the chlorination of a preformed pyridine ring. Chloropyridiries and a wide surprisingly we have found that chloropyridines may be prepared directly by chlorination of e-caprolactam or its isomer cyclohexanone oxime, starting materials which are established intermediates in the large-scale manufacture of Nylon-6. Thus according to the present vided a process for the manufacture of a chloropyridine which comprises interacting e-caprolactam or cyclohexanone oxime with chlorine in the vapor phase The chlorination reaction is. preferably carried out at a temperature of at least 250 C, preferably in the range from 400to600C. t

it is preferred to preheat separately the feed of chlorine and the feed of the caprolactam or cyclohexanone oxime; I

The reactants may be diluted with inorganic diluents, for example nitrogen and/or steam, or with organic HALOGENATED PYRIDINE prepared, for example, b 'yj vphotooximation "of nitroe-caprolactam by means of a Beckmann rearrangeinvention there is prodiluents, preferably inert towards'chlorine, for example carbon tetrachloride. When a gaseousor volatile diluent is used the caprolactam or cyclohexanone oxirne starting material may-be vaporized in thestream I of diluent vapor which serves as a-carrier gas; when a liquiddiluent is used,'the caprolactam or cyclohexanone oxime material maybe'dissolved in the liquid diluent and the resulting solution may then be vaporized as a whole. v The process is especially applicable to the production of pentachloropyridine but chloropyridines containing fewer than five chlorine atoms may also be obtained, the proportion of such products depending upon the-proportion 'of chlorine employed, the reaction temperature and the residence time;

In general, it is preferred to use at least 5 moles of chlorine per mole of caprolactam or cyclohexanone oxime. When pentachloropyridine is desired as the main product it is especially preferred to. use 'at least moles (for example from to moles) of chlorine per mole of caprolactam" or cyclohexanone oxime. ln

chlorine will be governed by economic'considerations. v

The reaction may be carried out in the absence of a catalyst, but a catalyst may be present ifdesired, for example a porous material'comprising silica, alumina (or cyclohexane, which may itself be prepared by nitration of cyclohexane. Cyclohexanone oxime is itself a precursor of e-caprolactam and may be converted into ment. I

Thedesired chloropyridine(s) may be isolatedfrom the reaction products by conventional techniques, for

example by fractional distillation, fractional crystallization, solvent extraction or a combination of such techniques.

The invention is illustrated but not limited by the following Examples:

EXAMPLE 1 49.2 ml of a solution of caprolactam (11.3 g) in carbon tetrachloride (92.4 g) was fed at a rate of 0.7 nil/min to a packed vaporizer maintained at 320 C.

. The issuing vapors were passed'to a vertical glass tubular reactor of l-inch bore held at a temperature of 530 C (:t 10 C) where they were mixed with chlorine fed at a rate of 0.47. liter/min measuredat20 C. The gaseous carbonttrachloride gave substantially pure pentachloropyridine.

' v EXAMPLE 2 I p r 49.2 ml of a solution of e-caprolactam-(l 1.3 g) in carbon tetrachloride (92.4 g).was fed at a rate of 0.8

ml/min to a packedvaporizer maintained at 300 C.

The issuing vapors were passed to a vertical glass tubulai reactor of 1-inchv bore ,held at a temperature of 400 C 1 10" where they were mixed with chlorine fed at a rate'of 0.57 liter/min measured at- 20 The gaseous feed to the reactor contained Q I moleslof carbon tetrachloride and 20 moles of chlorine per mole of caprolactam: the residence timewas 10 seconds. The gaseous reactor effluent was condensed and collected in cooled carbon tetrachloride. ',lhe resulting carbon tetrachloride solution was distilled to remove solvent caprolactam fed) together with 2,-chloropyridine 8 a mixture or combination of silica and alumina) or car- 7 bon.

Convenient residence times of the mixture in the reaction zone are, for example, between 10 and 30 seconds, but higher or lower residence times may be used if desired.

. ml/min to a packed vaporizer maintained; at 300 C.-

percent) 2,4,6-h'ichloropyridine 10 percent), 2 ,3,6-

trichloropyridine ('3-' percent), 2,3,4,6- 'tetrachloropyridine (l3 percent) and 2,3,5,6-

tetrachloropyridine (1 percent).

EXAMPLE 3 46.6 ml of a solution of cyclohexanone oxime(l 1.3' g) in carbon tetrachloride (92.4 g) was fed at a'rate of 0.7

The issuing vapors were passed to a vertical glass tubu- C i C where they were mixed with chlorine fed at a rate of 0.46 liter/min measured at C. The gaseous feed to the reactor contained 6 moles of carbon lar reactor of 1-inch bore held at a temperature of 550 tetrachloride and 18 moles of chlorine per mole of 5 1. A process for the manufacture of a chloropyridine 2O which comprises interacting e'caprolactam with chlorine in the vapor phase at a temperature of at least 250 C.

2. A process as claimed in claim 1 wherein the proportion of chlorine is at least 5 moles of chlorine per mole of caprolactam.

3. A process as claimed in claim 2 wherein the proportion of chlorine is at least 10 moles per mole of caprolactam.

4. A process as claimed in claim 3 wherein the proportion of chlorine is from 15 to 30 moles per mole of caprolactam.

5. A process as claimed in claim 2 wherein the reaction temperature is in the range from 400 to 600 C.

6. A process as claimed in claim 2 wherein the reaction is carried out in the presence of a diluent.

7. A process as claimed in claim 6 wherein the diluent is carbon tetrachloride. 

2. A process as claimed in claim 1 wherein the proportion of chlorine is at least 5 moles of chlorine per mole of caprolactam.
 3. A process as claimed in claim 2 wherein the proportion of chlorine is at least 10 moles per mole of caprolactam.
 4. A process as claimed in claim 3 wherein the proportion of chlorine is from 15 to 30 moles per mole of caprolactam.
 5. A process as claimed in claim 2 wherein the reaction temperature is in the range from 400* to 600* C.
 6. A process as claimed in claim 2 wherein the reaction is carried out in the presence of a diluent.
 7. A process as claimed in claim 6 wherein the diluent is carbon tetrachloride. 